Slvr77

After reading all the timing guides I could find, including Lars papers, and foolishly thinking I had an actual understanding of the process....

I cannot get my Stock (minus emmissions and with true dual exhaust if that matters) '77 L82 timing to match any of these guides.

Just looking at Base timing, my numbers do not make sense. I have only had the car for a year at this point, and do not know what previous owners have done with the timing curve. So to start I plugged the VAC line, and took a reading.

Per my service manual, factory Base timing should be 12* btc at 700rpm

Keeping that in mind here is what I found:

Before I touched the timing: 700rpm - 22* btc

"All in" by 1700 to 1800rpm - 44* btc

That was before I touched it I have driven the car for a year and have not noticed knocking.... how can that be ?!? These readings came from my adjustable dial timing light, and the light seems accurate compared to my Dads old fixed timing light using the markings other than "0"


So then I touched it I took the rotor cap off and inspected the weights and bushings, they looked worn and everything was dirty. I purchased a Mr. Gasket 929g timing kit, and swapped out the weights and springs and bushings, cleaned everything up. I even started with the strongest springs in the kit, as I wanted to just get my Base Timing back to 12* as a start.

Check timing with new weights and stiff springs, it was at 24 - 26*, so I turned the distributor to lower it back to 12*

After playing with the idle mixture screw on my quadrajet and rotating the distrbutor I arrived at 12* at 700 rpm. I even verified that the stiff springs were holding things, at 1200 rpm there was no change, still 12*

At this point things seemed to be going well (per Lars papers). I bumped my idle back up to 800, as these readings were in park. Normally when I drop it in drive, the RPMs drop about 150 ... so 700 was too low in park to keep it running while in drive.

I then started to notice a strange issue.... when I put it in drive, my RPMs went down to 600 or so, a normal number I get sitting in traffic and such, but the car would not stay running, after 30 seconds the idle would slowly go down to 500 get very rough, and continue to drop to the point of stalling.

Questions:

Should a stock L82 of this year idle at 12* of base timing ? Am I misled by the Service manual specs ?

Why would it idle fine at 700rpm (in park) with this timing, but when the transmission load was added I could not keep it running without holding the RPMs up?

Did the previous owner know something I don't that made him push the base timing up above 20* (and yes the VAC is plugged off)?

Finally I can't believe there was no knocking at over 40* timing "all in" ... not every stop sign sees a WOT pull away on my part but still.

And I did triple check I had my light connected to cylinder "1"

scottyp99

Hmmmm, maybe you should go back and re-read Lars paper on how to set timing, because what you are doing has nothing to do with his method of setting timing.

First of all, don't worry about the "base timing". It doesn't mean anything, as long as it's roughly between 12 and 18. Set the "all in" timing first, at 2500-3000 rpm. It sounds like you could have done this by backing the distributor off 8 degrees, and installing heavier advance weight springs. 22-8=14, 44-8=36, heavier springs slows down advance curve to 3000 instead of 1800 rpm.

Put the original advance weights back in, try the medium springs from your 929g kit, set initial timing at 14 degrees, and see how your curve looks. Adjust the idle screws using a vacuum gauge (adjust to highest vacuum at desired idle rpm) and let us know how it's going. Good luck,

Scott

aussiejohn

Slvr77,

My white '74 coupe was impossible to time. When I bought it, it ran fine, but an oil leak at the rear of the inlet manifold necessitated the removal of the manifold (and of course the dissy!) so when I put it all back together, I just could not get it to run.

Long story short, I finally discovered that the outer iron ring on the balancer had slipped and the timing mark was nowhere near in the right position. So I just set the timing by ear and although not perfect, the car runs well.

I have since purchased a Powerbond unit (Made in Australia!!! Oops, Wrong flag; where's the Aussie one?) and will fit it when I can find the time. I have a cast aluminum timing cover (also made in Australia) that I will fit at the same time.

So, check to see if the outer ring of your balancer is in the right place. If it's not, then all of the work you have done is for nothing.

Hope this helps.

Regards from Down Under

aussiejohn

Ralphbf

The way I've timed cars for years is simple.

Take it out in the country loosen the distributor so you can barley turn it.

From a complete stop floor it.
If it rattles retard the timing, if not advance the timing.

For best mileage let it rattle a little.
If you do this then you should not let it rattle.
Meaning never accelerate hard.

For the best power back it up until it just quites rattling.

Preignition is hard on an engine and should always be avoided.
Early or retarded timing robs power and fuel economy.

Also there is a point where the engine runs good but starts hard.
For this you need a broader advance curve.
One that will be retarded enough to let the engine start easily but be able to advance enough for good power and good economy.

Give it a try you have nothing to loose.

Ralph

jb78L-82

I had trouble setting my base timing to the factory specs for years and could never do it. I followed the "Info on Timing-Long Post" thread by BarryK and was finally able to get the timing correct so that it was all in by 2,500-3,000 RPM and it has been perfect since. Don't worry so much about the base timing since the total timing is what is important! Hope that helps!

noonie

You won't get the stalling while sitting in traffic if you set the curb idle to 600 in Drive as per the GM specs. An auto will drop when put into gear.

It's a good thing to check the mark on the balancer ring with #1 at TDC and remark it if necessary. Then you can retime using whatever instructions you are happy with. The GM weights and springs will not give the max advance the wieghts and dist cam are capable of.

DanielA

I can't deal with all your issues, but I experienced some of them with my 77 L82. My base timing was at 12 too, but when I reved it up it was all in at around 1800 and only about 28 degrees. Based on the various articles, I was shooting for 36 at 2500-3000.

I played around with the MR Gasket kit, but even using the strongest springs with the factory weights it was still all in at only 1800 rpm. I also tried the Mr gasket weights to see if they gave more mechanical advance, but to no avail.

I posted to this forum, and evidently those are the correct advance numbers for our cars. That is, the distributor only provides about 16 degress of mechanical advance and it comes in quick.

I set mine at 34 all in which gives me a base number at idle of about 18. I could have gone all the way to 36, but it seemd that having the initial timing at 20 was getting a little excessive.

Any way, the car runs great at that setting. No pinging and better power than the factory setting. By advancing the timing, the idle speed incresed, so I had to re-set the idle speed on the carb. I am at about 900 in neutral and 700 in drive and it idles fine.

Hope this helps.

Slvr77

Thanks for all the replys!

I took another try at it today and this is where I got:

Using the entire Mr. Gasket 929g kit (weights bushings and springs) I selected the least stiff springs of the bunch (black color). Mr. Gasket claims the black springs start advancing at 1000RPM and then are all in by 2400 or so (atleast thats what the graph shows)

Similar to DanielA I set the base timing up to 18* at 700RPM as 12 just was not working. I then checked at 2400RPM timing was 30* I took it to 2700RPM and timing was 32* and it did not seem to go higher.

Best I can tell I am only getting 14* of advance with these weights even with the lightest springs. The car ran fine with these settings, so wanting to get close to 36* not 32 ... I moved base timing another 2* up to 20. Still running fine my 2700 RPM reading was 34*

I test drove the car and it seemed fine, I think I noticed better throttle response but it could have been in my head

Any reason why I am only seeing 14* of mechanical advance ? Every guide seems to point at 24* of advance... and Im still not sure why the car likes 18 or more degrees timing at idle.